Brooklyn Heights residents are muscling up in their effort to defeat Mayor Bill de Blasio’s more-than-$3 billion plan to rebuild the two-level highway that supports the Brooklyn Promenade.

Over the past three months, neighbors have joined forces to create A Better Way, a non-profit whose sole purpose is to defeat a repair plan that could take the beloved Promenade out of service for up to six years and put a six-lane highway in its place.

“Putting a highway through a neighborhood is a hard proposition these days,” said Jon Orcutt, the former policy director at the city’s transportation department. “And if you do it in an old money neighborhood, it’s a harder proposition. But I think there’s more people than just Brooklyn Heights NIMBYs that think the city should be coming up with something better.”

The self-described “accidental activists” who built A Better Way are counting on it.

In recent weeks, the group retained a high-powered lobbying firm, Capalino and Company, and a well-connected communications firm, Mercury Public Affairs, to advocate on its behalf. It’s met with Brooklyn Borough President Eric Adams and staff from Comptroller (and likely 2021 mayoral candidate) Scott Stringer’s office. Stringer last week sent a letter to the mayor decrying what he described as de Blasio’ failure to pursue options that would minimize disruption to the neighborhood.

The group, which coalesced in the wake of a heated September 27 meeting hosted by the city, is only just now getting started. Its leadership trifecta includes former Assistant U.S. Attorney for the Eastern District Hilary Jager, professional organizer Ann Dooley and real estate executive Sabrina Gleizer.

They’ve started a website, incorporated as a non-profit and begun raising money. They won’t say how much, but it’s enough to hire Mercury, which represents firms like Charter Communications, and Capalino, whose clients include Airbnb and the Brooklyn Bridge Park Conservancy.

The group touts more than 750 volunteers and support from some 47 co-op boards. (Prominent Brooklyn Heights resident and former MTA chairman Joe Lhota, who famously said the city’s plans had turned him NIMBY, has yet to join up.)

“It’s true that we are a resourced community, but I don’t think the fact that we are coordinating and coming together to oppose this plan is a reflection of that,” Jager said. “I think it’s a reflection of the ill-conceived plan … If this were happening in other parts of New York City, people would talk about it and fight it.”

The BQE project has been in the works, on and off, for nearly a decade. New York State originally intended to conduct the repairs, until — to the surprise of community members — it abruptly withdrew in 2011. The de Blasio administration has reluctantly picked up the pieces and in September unveiled its proposal to the media. It involves building a six-lane highway where the promenade now stands to accommodate the 150,000 vehicles that traverse that portion of the BQE every day.

The city says the Robert Moses-era highway is so deteriorated it will no longer be able to carry trucks in 2026. The city wants to start construction in 2020 or 2021.

Transportation Commissioner Polly Trottenberg has not minced words about the difficulty of the project. She’s described it as an “epic challenge” and compared it to Boston’s Big Dig.

But neighborhood residents say the city has not been transparent.

Trottenberg spokeswoman Alan Morales said, in a statement, “We are in the middle of extensive engagement with the community to ensure the BQE reconstruction is as transparent as possible, and any claim to the contrary is demonstrably false. We have held a number of meetings with stakeholders — including A Better Way itself — and will be hosting additional meetings with neighborhood businesses, residents, and groups.”

She also said the environmental review process, which is about to begin, will explore other options too.

In the meantime, Brooklyn Heights residents are exploring their own options.

“We really think this is an opportunity to shine a light on bad decision making,” Gleizer said.